Method for mining oil shales, tar sands, and other minerals

ABSTRACT

In the mining of subsurface friable mineral ore deposits, the invention provides a mine configuration and mining system wherein the mine has preferably three levels. The first operating level, is positioned substantially at the base of the deposit and has an interconnecting system of tunnels within which, mining apparatus operates. This level further includes conveyors adapted to receive loose ore and transport same to vertical shafts or ore passes which interconnect adjacent operating levels. The second operating level is primarily a collecting level, and is positioned below the first, or mining level, to be parallel therewith. This second level has a tunnel system operatively associated with the vertical ore passes of the first level, and has conveyors which collect the loose ore and carry same to shafts for transport to a final, lower level, from which the ore is removed from the mine. According to the invention, active mining is carried out by the known &#39;&#39;&#39;&#39;Fixed Arch Shield&#39;&#39;&#39;&#39; technique on only one level, the only other levels being ore collecting and haulage levels. There are no levels, or mine workings, above the first, mining level, only access and ventilation shafts. By utilizing this mining method and the preferred mine configuration, a complete ore deposit can be removed with minimal surface disturbance, and subsidence can be compensated for by distributing waste in a manner that is esthetically acceptable.

United States Patent Johns June 10, 1975 l l METHOD FOR MINING ()ll.SHALES. TAR

SANDS, AND OTHER MINERALS Primary ExaminerErnest R. Purser Attorney,Agent, or FirmMcl..aws & Company {57] ABSTRACT In the mining ofsubsurface friable mineral ore deposits, the invention provides a mineconfiguration and mining system wherein the mine has preferably threelevels. The first operating level, is positioned substantially at thebase of the deposit and has an interconnecting system of tunnels withinwhich, mining apparatus operates. This level further includes conveyorsadapted to receive loose ore and transport same to vertical shafts orore passes which interconnect adjacent operating levels. The secondoperating level is primarily a collecting level, and is positioned belowthe first, or mining level, to be parallel therewith. This second levelhas a tunnel system operatively associated with the vertical ore passesof the first level, and has conveyors which collect the loose ore andcarry same to shafts for transport to a final, lower level, from whichthe ore is removed from the mine. According to the invention, activemining is carried out by the known Fixed Arch Shield" technique on onlyone level, the only other levels being ore collecting and haulagelevels. There are no levels, or mine workings, above the first, mininglevel, only access and ven' tilation shafts. By utilizing this miningmethod and the preferred mine configuration, a complete ore deposit canbe removed with minimal surface disturbance, and

subsidence can be compensated for by distributing waste in a manner thatis esthetieally acceptable,

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PATENTED JUN 1 0 i975 SHEET SHEET PATENTEDJUN 10 I975 ll j METHOD FORMINING Oll. SHALES. TAR SANDS, AND OTHER MINERALS BACKGROUND OF 'lHl: INVIZNTION This invention relates to the mining of "oil shales" as foundin Colorado, Wyoming. and ltali. U.S.A.. and similar deposits of coal,oil shales. oil sands and other minerals found elsewhere.

The mining of oil shales appears to be the most imminent application ofthis method and, within the context of this application, mention is madeof oil shales to the practical exclusion of other minerals. It should beunderstood that. wherever oil shales are mentioned, reference could bemade to other minerals.

The term oil shale" refers to sedimentary deposits of organic-richargillaceous dolomites and marls. The organically derived component is ahydrocarbon called kerogen." a mineral that when heated to asufficiently high temperature is converted to a form of crude petroleum.Deposits of oil shale. occurring principally in the States of Colorado.Utah and Wyoming, U.S.A.. contain billions of barrels of crude oilreserves.

The U.S. Bureau of Mines estimates that 81 billion barrels of liquidfuels will be required for consumption in the immediate future. This ismore than was produced in the United States during the 100 years afteroil was discovered in 1859. Oil shalcs are therefore a logical source ofa substantial portion of this requirement.

While the oil shales constitute a resource. they cannot be utilizeduntil some means is developed which will allow its exploitation withsafety and economy. The deposits of oil shale are enormous but they arealso low-grade containing only a very small amount of oil per ton andthis means that the cost of mining a ton of raw shale ore must berelatively low to make the work economically justifiable.

Investigations to date have been of a pilot basis. These include theplant operations of Union Oil Co., the U.S. Bureau of Mines, the ColonyDevelopment Company joint venture, etc., but an economically viablemethod has not yet been demonstrated.

There has been a voluminous amount of publication on the subject ofmining oil shales. Reference of interest, to list only a few include:

I. Methods for Mining Deep, Thick Oil Shale Deposits," Whiting, J. M.U.S. Pat. No. 3.588,l75, dated June 28,1971;

2. Prospect for Oil Shale Development, Colorado, Utah and Wyoming, U.S.Department of the Interior, Washington, DC, May I968;

3. Allsman, P. T., A Simultaneous Caving and Sur face restoration SystemFor Oil Shale Mining. Ouarterly of the Colorado School of Mines. Golden,Colo, Vol 63, No. 4. Oct. 1968. pp. ll3l26, and:

4. Cameron and Jones. Inc. Comments and Suggestions on the Department ofInterior Oil Shale Policy Statement of May I968, "Synthetic FuelsQuarterly Report, Cameron and Jones. lnc.. Denver. Colo.

Most of the attempts at mining oil shales have been by the conventionalroom-and-pillar method in relatively thin strata. This is applicable tonear-surface oil shale deposits which have a thickness from 20 topossibly I feet. Beyond a thickness of 100 feet, the rooms become toohigh to be worked by normal room-and-pillar methods. the method becomesvery dangerous and nearly 50 of the oil shale must be left in pillars.The oil shale deposits are very thick and removing I()() feet from anypart of that thickness, while destroying the remainder for practicalmining. is not acceptable.

It has been suggested that the thick oil shale strata could be minedsuccessfully by open pit methods. While technically possible. themagnitude of the open pit and the enormous pile of tailings would beecologically unacceptable even though the open pit might eventually befilled in and become esthetically acceptable.

A variation of block caving method has been suggested for extractingdeep thick strate of oil shale, (Allsmam P. T. A Simultaneous Caving andSurface Restoration System For Oil Shale Mining, lbid.) The majorobstacle to this appears to be the lack of control of caving.

Another possible mining method, referred to as cut' and-fill has beensuggested and forms the basis of the previously mentioned U.S. PatentSer. No. 3,588,175.

All of these methods have been considered and investigated and found tobe either too hazardous or too expensive. In most cases they are bothhazardous and expensive. Possibly of equal importance is that they havenot been esthetically acceptable to the conservationists and ecologistswho are very jealous of the semimountainous area in which the depositsoccur.

Accordingly, the primary objective of the present invention are to:

a. remove the oil shale at a cost that is commercially acceptable forproduction of crude oil;

b. increase the safety of the miners excavating the oil shale, and;

c. conduct the excavation and disposal of waste in a manner which willbe innocous. and barely discernable to anyone.

BRIEF DESCRIPTION OF RELATED APPLICATIONS The present applicant. in U.S.Patent Application Ser. No. 509,489, filed September 26, 1974, teacheswhat is referred to hereafter as the Fixed Arch Shield technique formining oil shale, and tar sands.

Briefly, this technique provides a mining method that only requiresactive mining on a single level, at the base of an ore block tosubstantially remove lOO% of the mineral block.

This technique involves establishing a laterally extending undergroundmining face of perhaps 1,000 feet in width and from 10 to 12 feet inheight, against which a laterally extending mining shield is positioned,the shiled serving to partially enclose mining machinery such as lateralshearing ploughs, rotary cutters or the like which are conventional inunderground coal mining, the cutter operating across the full width ofthe mining wall. The mined material. after being cut from the miningface. falls onto a lateral conveyor operating within the mining shield,and is then conveyed from the face to collecting means, operating at theends of the face for ultimate conveyance through a shaft to the groundsurface.

The mining shield comprises a plurality of individual arch sections.each individually advanceable towards the mining wall as the mining wallrecedes, thereby creating a void posteriorly of the mining shield.leaving the back" unsupported and permitted to collapse. Normally. theback will not subside for several hours after the advance of the shield,due to the semiplastic" nature of the sand and the entrained viscousbitumen. Under normal mining operations, the back will collapsegradually, to 40 feet behind the moving mining shield as it advancesinto the bituminous sand body.

The operation will proceed for an optimum distance of forward travel,and is then repeated, to operate on the collapsed material as before. Itwill be appreciated that the entire operation takes place on, oradjacent the basement rock, the operation proceeding until the desiredsection of bituminous sand has been mined out.

The cutting equipment is not manned, the cutter travelling between apair of operators, one at each end of the assembled movable shield eachsuch operator being positioned in a pulpit in permanently supportedmanways.

Apparatus is also disclosed in the prior application for attachment tothe mining machine in order to adapt it to the specific requirements ofunderground bituminous sands mining, in which a pair of cleaner ploughsare retractably secured to the mining machine at each end thereof, foralternate action in following relationship to the mining machine and inleading relationship to the advancing apparatus for the mining archsections, the purpose of which is to remove spalled detrital from thefresh cut which might otherwise impede the forward movement of themining arch sections.

Apparatus is also disclosed for indexing the mechanism for advancing themining arch sections.

It will be appreciated that the method of this prior invention is, ineffect, a combination of longwall mining, which is characteristic ofcoal mining, and block-caving, which is characteristic of hardrockmining, in which the bituminous sand body is continuously block cavedbehind the advancing undercut of the longwall face, until the bituminoussand body is completely mined out, there being no attempt made tosupport the backs.

In the present application, therefore, a principle objective is also toprovide a mine configuration and mining system which adapts readily tothe application of the Fixed Arch Shield" technique of mining subsurfaceore deposits.

SUMMARY OF THE INVENTION Accordingly the present invention provides amine configuration having at least two, but preferably three tiers, orlevels. The upper of mining level positioned at or near the base of theore deposit, comprises a tunnel system including peripheral servicetunnels bounding the mining zone, a central access tunnel and aplurality of transverse tunnels extending from the central access tunnelto adjacent service tunnels. The transverse tunnels preferably runparallel one to the other and effectively divide the mining level into ahorizontal series of contiguous mining blocks. Each block is mined aswill be described hereafter by the Fixed Arch Shield" method, the orebeing conveyed from the face of the block to the transverse tunnels,from where it is transported to vertical shafts, or loading chutes whichconnect with a lower level of the mine.

In addition to the single mining level, preferably two lower operatinglevels are contemplated by the invention. Whether in fact a double ortriple mine is developed depends largely on the topography of the area,size and depth of the ore deposit or type of mineral being mined. Allthese factors relate to the total cost of operating and consequentlyhave a direct bearing on the final mine configuration.

In the case of two tier mine, the lower, second operating level has thefacility for collecting ore passed downwardly from the mining level viavertical ore passes, or chutes, and for transporting the ore to thesurface.

More preferably, however, the invention invisages a three-tier mineconfiguration having a mining level as previously described; a secondlower operating level which acts as a collecting and conveying levelonly, and; a final third, still lower operating level which has thefacility for large scale haulage and removal of the ore from the mine.Each level is interconnected by ventilation shafts, and supply shaftswhich include surface transportation apparatus, and the referred toloading chutes and ore passes which are located on all levels, atpositions which are predetermined by the layout of the tunnel system,and ore conveyors.

Accordingly, a preferred embodiment of the invention will now bedescribed, by way of example only, reference being had to theaccompanying drawings which depict a three-tier mine configuration andthe operation thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, is a schematic plan of a thirdlower level showing the layout of haulageways, loading chutes. supplyand ventilation shafts;

FIG. 2, is a schematic plan of a second, transport and collecting levelshowing the layout of the major collecting tunnels which serve to conveythe broken ore to the loading chutes,

FIG. 3, is a schematic plan of a first upper, or mining level, with acentral access tunnel and periphery service tunnels related to thesupply and ventilation shafts;

FIG. 4, is an enlarged, sectional view along line B B ofFIG. l and A Aof FIG. 3, showing the three levels, loading chutes, ore passes, oilshale and overbur den;

FIG. 5, is a schematic plan ofa transverse tunnel on the mining level,between production blocks, the central access tunnel and the peripheryservice tunnels;

FIG. 6, is a schematic, enlarged plan of a portion of FIG. 5 withproduction blocks between transverse tunnels extending from centralaccess tunnels;

FIG. 7, is a schematic, enlarged plan of same area as FIG. 6 showingfirst mining cuts advancing from the central access tunnel in sixproduction blocks;

FIG. 8, is a sectional view along line C C, of FIG. 7 and shows the oilshale subsiding into the space be hind advancing production faces andthe subsidence of overburden at the surface filled by waste;

FIG. 9, is a schematic enlarged plan of same area as FIG. 7, showingsubsequent cuts following along the production blocks from the centralaccess tunnel;

FIG. 10, is a sectional view along line D D, of FIG. 9, with the firstcut advanced and a second cut following the first.

FIG. 11, is a schematic plan of the same area as depicted in FIGS. 5, 7,9, with production faces far advanced and a fifth cut following earliercuts;

FIG. 12, is a sectional view along line E E of FIG. I] with fivesuccessive cuts started and following earlier cuts;

FIG. I3, is a sectional view along line E E of FIG. 11 with 20successive cuts started and following previnus cuts, oil shale suhsidinginto spaces behind advancing production faces and subsidence ofoverburden at surface filled with waste;

FIG. 14, is a sectional view along line F F of FIG. 11 and at rightangles to FIG. 13 with some twenty suecessive cuts started;

FIG. 15, is a perspective view of the lining utilized in the transversetunnels, having arches of steel or other material.

FIG. I6, is a perspective view showing relationship of the tunnels inthree levels and the interconnecting ore passes and loading chutes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As previously indicated. thisinvention is primarily suited for recovery of deep thick mineraldeposits such as oil shalcs, coal and other minerals. Accordingly.property should be purchased to provide sufficient ore reserves within asingle rectangular tetragonal block or prism, although irregular blockscan be accommodated.

Because of the diversity of access and topography related to the manyoccurrences of oil shalcs in the Western U.S.A., no attempt will be madehere to show access, Access to the underground workings could be byshafts, declines, adits or a combination of these.

Because of the tremendous tonnages involved, either full sized railwayhaulage or large-sized belt conveyors are indicated for use as thehaulage medium.

By means known per se. access is provided to the base of the oil shales.

Mining begins as close to the base of the oil shales as can be attained,and begins at, and advances from, the center of the property and spreadsin all directions from the center.

The most desirable features of this invention are in the control ofproduction, and surface subsidence; the control of the surfaceindication of subsidence, and in the provision of a safe workingenvironment. The mining machinery in the Fixed Arch Shield" is remotelycontrolled by the operator who is always protected by massive steelstructures and remote from the actual cutting face and scene ofoperations, and does not have to come into contact with the ore at anytime.

Subsidence of the oil shale and overburden follows the advance of themining apparatus, and spreads out from the center of the property. Thedegree of subsidence has no effect on the recovery from the surroundingproperty. The underground workings may be expanded, as required. or acompletely separate operation commenced exactly at the limits of miningof the first operation.

Recovery of the oil shale. that is oforc grade, is invisaged as close toIO%.

Referring to the drawings in general;

Ventilation raises or shafts 36 are installed at the approximate fourcorners of the property. Exemplary distances between might be that thedimensions indicated, Y, would he miles.

The Mining Zone" is centrally located within the rectangle ofventilation shafts 36. The mining zone being that volume of oil shale,within the property. which is undcr active mining operations. Exemplarydi mensions might be that. in a square block 5 miles by 5 miles inextent. the mining zone might be 4 miles by 4 miles with /2 mile aroundthe sides reserved as a 'fender" against the lateral spread ofsubsidence from the underground workings within the mining zone.

At a section substantially bisecting the mining zone,

a pair of access and supply shafts 26 would be installed 5 at the outerboundary of the property.

Referring specifically to the drawings:

FIG. I, is a plan of a main haulage level driven beneath the miningzone. This level is driven in a known manner at the base of the oilshale, or preferably, below the ore zone. The tunnels which constitutehaulage level 20 are driven outwardly from a central access tunnel 35which also serves as a ventilation tunnel. and are spaced at a distanceW, apart. Exemplary dimensions might be that W could be I% miles,although the spacing will be such as to give maximum service withminimum cost. At regular intervals governed by the most advantageousloading requirements, loading chutes 22 are installed in the haulagetunnels 20.

The haulage level 20, along with all other levels would be connected tothe shafts 26 and 36 by suitable manways for emergencies but, forventilation, the shafts 26 would be intake," and the shafts 36 exhaust."

FIG. 2, depicts a collecting and gathering level 21, driven above themain haulage level. This second tunnel complex 21 is connected to themain haulage level 20 by the vertical loading chutes 22. The collectingand gathering level 21, consists of a network of tunnels 23 containingbelt or other conveyors, (not shown), converging on the loading chutes22. FIG. 2 is schematic and the actual number of tunnels 23 would begoverned by the optimum spacing of the ore passes from the mining levelabove.

The second level 21 is also the exhaust air level. It is connected tothe ventilation shafts 36 by tunnels 34, and the draft adjusted toproduce a negative air pressure throughout level 21.

FIG. 3, is a schematic plan of the first, or upper mining level 24,which is driven above the transport and gathering level 21. The mininglevel 24 consists of a central access tunnel 25 driven between the twoaccess shafts 26. At the limits of the mining block, periphery servicetunnels are driven from the central access tunnel 25. The peripheryservice tunnels 30 extend around the complete outer periphery of thedesired mining zone.

FIG. 4, is a sectional view, enlarged, along Line A A of FIG. 3, andLine B B of FIGS. 1 and 3, and shows the three levels 20, 21, 24,loading chutes 22, ore passes 31, oil shale 40 and overburden 39. Whenthese levels are installed, the mining zone is ready for production.

From FIG. 5, is can be seen that the mining zone is divided into aseries of production blocks 29. The width Z of each production block isdependent on the type of Fixed Arch Shield selected for the development.An exemplary dimension might be that Z=l000 feet. Transverse tunnels 27are driven between production blocks 29 such that they form the outerboundaries of the production blocks 29, and extend from the centralaccess tunnel 25 to the periphery service tunnels 30.

FIG. 6, is an enlarged portion of the plan of FIG. 5 and shows thetransverse tunnels 27 extending from the central access tunnel 25. Theproduction blocks 29, of width Z, are enclosed between the tunnels 27.

Mining begins at, and advances from, the center of the mining zone, onthe mining level, at a point approximately equidistant between theaccess shafts 26. A production block 29, bounded by transverse tunnels27 is selected as the location of the first cut.

The Fixed Arch Shield" technique for mining involves the taking of ahorizontal cut from a working face of each production block bymechanical mining machines operating within the Shield." The workingface extends between two transverse tunnels 27 and would, therefore,have length Z. The height of the Shield would determine the thickness ofcut and an exemplary thickness might be in the region of IO feet.

According to the present invention two Fixed Arch Shields are set up,back-to-back in the central access tunnel 25. The production face 28 is.initially, the side wall of the central access tunnel 25. The machineryin the Fixed Arch Shield excavates a slice of oil shale from the side ofthe central access tunnel and widens the tunnel 25 over the length Zuntil subsidence of the roof of tunnel 25 occurs.

The production face 28 advances by repeated slices being excavated fromthe face 28 as the Shield is continually moved up to the face 28,between the transverse tunnels 27 along the base of the production block29.

The oil shale material removed from the production face 28 is depositedon chain conveyors, (not shown) in the Fixed Arch Shield which also actas a track for the cutting machines, (not shown), as in standardlongwall mining procedure. The ore is conveyed horizontally along theface 28 to the transverse tunnels 27, transferred to belt conveyors inthe transverse tunnels 27 and conveyed ahead, away from the centraltunnel 25.

When a transverse tunnel 27 on the first or mining level 24 crosses atunnel 23 on the second level 21, a vertical ore pass" 31 is madeconnecting the two tunnels 27 and 23 so that the conveyor in thetransverse tunnel 27 discharges down the ore pass 31 onto the beltconveyor in tunnel 23. The ore is then conveyed to the loading chute 22.(ref. FIG. 16)

The development of the Fixed Arch Shield technique eliminates thenecessity for supporting the roof or back of the workings. As theproduction face 28 advances by the operation of the Shield, the roof 32,behind the Shield subsides into the void 33. Because the width Z of theproduction face 28 is large, there is no alternative but for subsidenceto occur. The amount of subsidence, from any one cut, is very limited.As an example, if the Shield is feet high, and Z approximately 800 feet,the subsidence would be l0/800 ft. which is a comparatively minutesubsidence and this would produce a limited amount of disturbanceimmediately above the roof.

When the roof is in contact with the floor, subsidence stops andconditions of equilibrium are re-established.

After subsidence is complete, the central tunnel 25 is re-excavated twomore Fixed Arch Shields are set back-to-back and then advanced outwardalong the production block to make a second cut, 42.

FIG. 7, is a schematic plan of the same area as FIG. 6 showing the firstmining cuts 41 advancing from the central access tunnel 25 in sixproduction blocks 29 on the mining level 24.

FIG. 8 is a sectional view along line C C, FIG. 7 with the movingproduction faces 28 producing the first cuts 41. Oil shale is shownsubsiding into the space 33 behind the production face 28 with thesubsidence 37 8 extending upward, and spreading out, through the oilshale 40 and the overburden 39.

FIG. 9 is a schematic plan of the same area as FIG. 7 but with the firstcuts 41 being followed by second cuts 42. More production blocks 29 areunder active operation and the area of operations is expanded both aheadand laterally from that shown in FIG. 7.

FIG. 10 is a sectional view along line D D, FIG. 9 with first cut 41advanced and second cut 42 following. The subsidence 37 in the oil shale40 and the overburden is more extensive and is being filled in at thesurface by waste, 38.

FIG. 11 is a schematic plan of the same area as FIGS. 5, 7, 9, at a moreadvanced stage of development when the production faces 28 are faradvanced with the fifth cut 45 following earlier cuts 44, 43, 42, (cut4] already advanced beyond the area). All production blocks are inactive development within the selected mining zone.

FIG. 12 is a sectional view along line E E of FIG. 1] with fivesuccessive cuts started and following others, again, oil shale 40 isshown subsiding into spaces 33 behind the production faces 28, and thesubsidence of overburden 37 at the surface filled with waste 38.

FIGS. 7 to 12 inclusive, therefore Show the progress of the removalofthe oil shale, the subsidence of the remaining oil shale and theoverburden, and the filling of the subsidence with waste.

FIG. 13 is a sectional view along line E E of FIG. 11 at a much moreadvanced stage when twenty successive cuts have been started and arefollowing the previous cuts. A large part ofthe oil shale in the miningzone has at this stage been removed from its original positionaccompanied by the infilling of a large amount of waste.

FIG. 14 is a sectional view along line F F of FIG. 11, which is at rightangles to line E E and to FIG. 13 with the same twenty cuts started, thesame amount of oil shale removed, same amount of subsidence, and thesame amount of infilled waste as shown in FIG. 13.

FIG. I5 shows the transverse tunnels as being lined with archesconstructed preferably of steel, or materials having similar properties.The movement of each successive production face 28 along the length ofthe production block 29, between the transverse tunnels 27, in the FixedArch Shield technique, is accompanied by movement and re-arrangement ofthese arches. The material above the arches is excavated so that thereis no build-up of pressure on the arches as the roof or back 32 subsidesbehind the production face 28.

Finally, FIG. 16 shown in perspective, the interconnecting of the threelevels, 20, 21, and the transverse tunnels 27 of the mining level. Theangular relationship of the tunnel system may be chosen to suit aparticular mining zone, and therefore is not limited to theconfiguration shown.

The lining of multiple arches. FIGS. 15 and 16, remains in thetransverse tunnels 27, behind the production face 28, as the productionface 28 advances along the production block 29, but is not occupied,(except for emergency escape). The tunnel 27 continues to provideventilation to the production face 28.

When a further pair of Fixed Arch Shields is emplaced, back-to-back, inthe central access tunnel 25, after subsidence and preparatory tostarting another cut along a production block 29, the transverse tunnels27 are again available for service of the production face 28 of the newcut.

When the production face 28 is l|tl\ anccd by the action of the Shieldthrough the length of the production blocks 29 as far as the servicetunnel 30. the whole Shield including all machinery. is removed andtransported via the service tunnel 3|) to the central access tunnelwhere the Shield is reset for a further cut.

The procedure of re-excavating the central access tunnel aftersubsidence. the setting up of two Fixed Arch Shields back-to-bacL andthe starting of a further cut is repeated as often as necessary to mineout the thickness ofoil shale. The number of times this must be repeatedis determined by the formula:

thickness of ore'- Number of successne Cuts Control of brecciation ofthe oil shalcs. rate of subsi dence. and the rate of production are allprovided by regulating the pattern of production blocks 29. includingthe width Z. by spacing the successive cuts closer or farther apart.(varying X. FIG. ll and by increasing the number of production blocks 29under active development.

Brecciation of the oil shale 40 is desirable for most ecomonical miningbecause it is just as effective as con ventional blasting techniques.but brccciation should be limited to the zone immediately above themining level 24 so that the whole mining zone does not become toopermeable to surface waters.

The subsidence due to a single cut is minor. Because of thecomparatively large area involved. the subsidence must extend tosurface. However. by the time the subsidence reaches surface it hasspread over an area approximately twice the area of the cut in theproduction block 29. It will also have only substantially half thevertical movement over this greater area. It is therefore manifest. atsurface. as a gentle subsidence that can only be detected by precisemeasurements.

A thin layer of tailings 38 is spread. on surface. over the subsidingarea. The spreading of tailings is continued as the mining and subsidingcontinues. The apparent effect on surface is that there is a continuousspreading ofa thin layer. There is no build-up of mountainous piles oftailings. Any increase in the volume of the tailings. over the volume ofunbroken ore, is absorbed in a slow and scarcely perceptable rise in thesurface level. As the depth of tailings increases. compaction of thetailings will occur which will largely nullify the expansion in volume.

As will be appreciated. a continual growth of annual plants. grasses.etc. can be maintained on the surface except for a very small portionwhere actual filling is in progress. The grasses can reseetl themselvesand seed ing is constant following filling.

While preferred embodiments of the invention have been shown. it isunderstood that the invention can be practiced in other ays. and that\arious modifications and changes can be made in active miningoperations which are within the spirit of the invention. and the scopeof the following claims.

What is claimed is:

I. In the mining ofsubsurfacc friable mineral ore de posits. a miningsystem including a mine having at least two operating levels.interconnected by shaft means, and spaced one from the other in thevertical direction. said system comprising:

a. a first operating level. positioned substantially at the base of saiddeposit. and having a tunnel complex adapted for the utilization of theFixed Arch Shield mining technique. which tunnel complex includes:

i. a plurality of service tunnels bounding a designated mining area;

ii. a main access tunnel centrally bisecting said mining area. and;

iii. a plurality of transverse tunnels equidistantly spaced in parallelarray, and extending from said main access tunnel to adjacent of saidservice tunnels. to provide communication therebetween, and to define amultiplicity of mining blocks. said level further including conveyormeans adapted to collect and transport said mined ore to said shaftmeans;

b. means for mining said deposit. and;

c. a second operating level positioned below said first level andparallel therewith, said second level having a tunnel complex linkedwith said shaft means; said level further including means operativelyassociated with said shaft means, adapted to receive ore passing fromsaid first level through said shaft means and to transport said ore fromsaid mine.

2. In a system for the mining of subsurface friable mineral oredeposits. a mine configuration having three operating levels.interconnected by a plurality of shaft means, and spaced one from theother in the vertical direction. said mine comprising:

a. a single mining level, positioned substantially at the base of saiddeposit. and having a tunnel system including:

i. a plurality of service tunnels bounding a designated mining area;

ii. a plurality of transverse tunnels equidistantly spaced in parallelarray, and extending from said main access tunnel to adjacent of saidservice tunnels. to provide communication therebetween. and to define amultiplicity of mining blocks, and wherein means are provided toseparately mine each of said mining blocks, said level further includingconveying means adapted to receive mine ore, and transport said ore, forpassage through a first section of said shaft means;

b. a second operating level positioned below said first level to beparallel therewith. said second level having a tunnel systemco-operating with said first section of said shaft means; meansoperatively associated with said shaft means to receive ore passingtherethrough from said first level; said means adpated for thetransportation of said ore through said level to a second section ofsaid shaft means. and;

c. a third operating level. positioned below said second level to beparallel therwith. said third level having a tunnel system co-operatingwith said second section of said shaft means, said level including meansoperatively associated with said second section of said shaft means.said means being adapted to receive ore passing therethrough from saidsecond level. and to transport said ore from said mine.

3. The system of claim 2 wherein said means for mining each said miningblock includes an arch shield extending between adjacent of saidtransverse tunnels and positioned across the face of each said block.which shield partially encloses mining machinery inll eluding: rotarycutting means adapted for reciprocating across said face; shearingplough means and; said means for conveying mined ore from said face tosaid transverse tunnels.

4. The mine configuration according to claim 3 wherein said shaft meansincludes separate ventilation ducting, supply ducting, and loadingchutes.

5. The system of claim 4 wherein a plurality of ventilation ductscommunicate with said second operating level, and means are provided toproduce a negative air pressure within said second level 6. The systemof claim 3 wherein the second level is connected to said third level byloading chutes positioned at predetermined locations. each tunnel ofsaid system converging on an adjacent of said chutes and provided withsaid ore conveying means.

7. A method of mining subsurface friable mineral ore deposits comprisingthe steps of:

a. designating a suitably sized mining zone;

b. forming a tunnel complex below said mining zone to constitute a mainore haulage level;

c. forming a tunnel complex spaced above and parallel with said mainhaulage level but substantially below said mining zone, to constitute anore collection and transport level;

d. forming shaft means for the passage of ore from said transport levelto said haulage level;

e. forming a single mining level at the base of said mining zone, abovesaid transport level;

f. designating a multiplicity of suitably sized blocks of ore forproduction on said mining level, and mining said blocks using a FixedArch Shield mining technique. and;

g. transporting mined ore from said mining level by conveying ore toadjacent shaft means; passing said ore from said mining level to saidhaulage level, and; removing said ore to ground surface.

8. The method of claim 7 including the additional step of providingventilation ducting to each operating level, and providing a negativeair pressure within the tunnel complex of said transport level.

9. The method of claim 7 including the additional step on controllingthe limit, degree, and amount of surface subsidence by dimensionaladjustment of said mining blocks, the regulation of the frequency andspacing of mining operations, and by mining in an outward direction fromthe center of said mining zone.

1. In the mining of subsurface friable mineral ore deposits, a miningsystem including a mine having at least two operating levels,interconnected by shaft means, and spaced one from the other in thevertical direction, said system comprising: a. a first operating level,positioned substantially at the base of said deposit, and having atunnel complex adapted for the utilization of the Fixed Arch Shieldmining technique, which tunnel complex includes: i. a plurality ofservice tunnels bounding a designated mining area; ii. a main accesstunnel centrally bisecting said mining area, and; iii. a plurality oftransverse tunnels equidistantly spaced in parallel array, and extendingfrom said main access tunnel to adjacent of said service tunnels, toprovide communication therebetween, and to define a multiplicity ofmining blocks, said level further including conveyor means adapted tocollect and transport said mined ore to said shaft means; b. means formining said deposit, and; c. a second operating level positioned belowsaid first level and parallel therewith, said second level having atunnel complex linked with said shaft means; said level furtherincluding means operatively associated with said shaft means, adapted toreceive ore passing from said first level through said shaft means andto transport said ore from said mine.
 2. In a system for the mining ofsubsurface friable mineral ore deposits, a mine configuration havingthree operating levels, interconnected by a plurality of shaft means,and spaced one from the other in the vertical direction, said minecomprising: a. a single mining level, positioned substantially at thebase of said deposit, and having a tunnel system including: i. aplurality of service tunnels bounding a designated mining area; ii. aplurality of transverse tunnels equidistantly spaced in parallel array,and extending from said main access tunnel to adjacent of said servicetunnels, to provide communication therebetween, and to define amultiplicity of mining blocks, and wherein means are provided toseparately mine each of said mining blocks, said level further includingconveying means adapted to receive mine ore, and transport said ore, forpassage through a first section of said shaft means; b. a secondoperating level positioned below said first level to be paralleltherewith, said second level having a tunnel system co-operating withsaid first section of said shaft means; means operatively associatedwith said shaft means to receive ore passing therethrough from saidfirst level; said means adpated for the transportation of said orethrough said level to a second section of said shaft means, and; c. athird operating level, positioned below said second level to be paralleltherwith, said third level having a tunnel system co-operating with saidsecond section of said shaft means, said level including meansoperatively associated with said second section of said shaft means,said means being adapted to receive ore passing therethrough from saidsecond level, and to transport said ore from said mine.
 3. The system ofclaim 2 wherein said means for mining each said mining block includes anarch shield extending between adjacent of said transverse tunnels andpositioned across the face of each said block, which shield partiallyencloses mining machinery including: rotary cutting means adapted forreciprocating across said face; shearing plough means and; said meansfor conveying mined ore from said face to said transverse tunnels. 4.The mine configuration according to claim 3 wherein said shaft meansincludes separate ventilation ducting, supply ducting, and loadingchutes.
 5. The system of claim 4 wherein a plurality of ventilationducts communicate with said second operating level, and means areprovided to produce a negative air pressure within said second level. 6.The system of claim 3 wherein the second level is connected to saidthird level by loading chutes positioned at predetermined locations,each tunnel of said system converging on an adjacent of said chutes andprovided with said ore conveying means.
 7. A method of mining subsurfacefriable mineral ore deposits comprising the steps of: a. designating asuitably sized mining zone; b. forming a tunnel complex below saidmining zone to constitute a main ore haulage level; c. forming a tunnelcomplex spaced above and parallel with said main haulage level butsubstantially below said mining zone, to constitute an ore collectionand transport level; d. forming shaft means for the passage of ore fromsaid transport level to said haulage level; e. forming a single mininglevel at the base of said mining zone, above said transport level; f.designating a multiplicity of suitably sized blocks of ore forproduction on said mining level, and mining said blocks using a FixedArch Shield mining technique, and; g. transporting mined ore from saidmining level by conveying ore to adjacent shaft means; passing said orefrom said mining level to said haulage level, and; removing said ore toground surface.
 8. The method of claim 7 including the additional stepof providing ventilation ducting to each operating level, and providinga negative air pressure within the tunnel complex of said transportlevel.
 9. The method of claim 7 including the additional step oncontrolling the limit, degree, and amount of surface subsidence bydimensional adjustment of said mining blocks, the regulation of thefrequency and spacing of mining operations, and by mining in an outwarddirection from the center of said mining zone.